One of conventional and known technologies to separate a desired (predetermined) gas from a mixed gas is a PSA (Pressure Swing Adsorption) method. The PSA method is a separation method that takes advantage of a fact that an amount of gas to be adsorbed by an adsorbent (adsorption agent) varies with the type of the gas concerned, and a partial pressure of the substance (gas) concerned. When the PSA method is used, a mixed gas is introduced to an adsorption tower, which is filled with an adsorbent, to cause the adsorbent to selectively adsorb a predetermined gas contained in the mixed gas (adsorption step). After the predetermined gas is adsorbed by the adsorbent, the predetermined gas is desorbed from the adsorbent (recovering or regeneration step). In the PSA method, a pressure difference is forcibly created between the adsorption step and the regeneration step to separate the predetermined gas from the mixed gas.
In recent years, a PSA method that uses an adsorbent made from a perovskite-type oxide is disclosed as a PSA method-based technology for efficiently separating oxygen from the air (for example, Patent Literature 1). According to the technology of Patent Literature 1, the adsorption step and the regeneration step need be performed at a high temperature such as 250-900 degrees C. For this reason, the adsorbent (adsorption tower) is heated to a predetermined temperature, and maintained at a prescribed temperature. In order to prevent the temperature drop of the adsorbent, which should be maintained at the prescribed temperature, there is provided a heater in the adsorption tower to heat the normal temperature mixed gas introduced into the adsorption tower such that the heated mixed gas contacts the adsorbent.